1. Field of the Invention
The invention relates to a roller reefing boom system, a mast track arrangement, a sail and a rig for use in said roller reefing boom system.
2. Discussion of the Background
During the past few years, particularly on sailing yachts of more than 40 ft in length, roller reefing systems for the mainsail have come into use, because these roller reefing systems have the advantage over the conventional jiffy reef that smaller crews are able to safely and easily reduce the sail area.
Principally two roller reefing systems are distinguished. In the case of the roller reef used most frequently at present, the sail is furled around a furling means provided in the mast profile (furling mast). This system has the drawback that the weight of the mast is increased. The increased top weight of the mast particularly entails a reduction of the righting moment so that the yacht can carry less sail area particularly on the wind.
Moreover such a construction is not adapted to make use of a full-batten mainsail, because the battens make it impossible to furl the sail around an axis parallel to the luff.
For the yachtsman this furling system has the additional drawback that the sail shape varies due to furling into the mast so that no optimum flow of the sail shape is ensured when the sail is partly reefed.
Hence, roller reefing boom systems, as they are called, have been developed in which the mainsail is furled around the boom. To this effect, the boom is fixed to a swivel-fitting and can be rotated about its axis of rotation by an actuating means. This rotation of the boom is effected by an appropriate mechanism which is manually operated in the case of smaller yachts (less than 40 ft), while on bigger yachts usually hydraulic systems are employed.
The furling boom has the advantage that also full-batten mainsails can be used, because the battens are normally disposed parallel to the axis of the boom. Moreover, when used in a roller reefing boom system, the mainsail can have a roach, especially in the top area, because the furling is effected approximately around the axis formed by the straight foot, whereas in the case of furling mast systems the leech of the sail must be substantially straight so as to guarantee even furling into the mast and a relatively effective shape of the reefed sail.
Since the means required for rotating the roller reefing boom and the furled portion of the sail are arranged relatively closely to the center of lateral resistance of the yacht, the righting moment of the sailing yacht is only slightly impaired. Thus the roller reefing boom permits, in comparison to a furling system in which the mainsail is furled into the mast, a larger sail area with the same keel weight.
In the previously known roller reefing boom systems the mainsail has been guided in a slot in the mast. In order to be able to take up the forces occurring when trimming the sail, the luff rope must have a predetermined minimum diameter so as to hold the sail reliably in the mast slot. If the luff diameter is too small, the sail may be pulled out of the slot or may be clamped in the same in the case of extreme mainsheet tensions so that it is very difficult to reduce the sail area.
A large diameter of the luff rope has the drawback that the furled sail layers are not close to one another in the luff area but need considerably more space compared to the furled sail in the leech area. This may result in an uneven furling of the mainsail.
Hence, on the one hand there is the demand to design the portion of the mainsail guided in the mast slot as strongly as possible so as to take up the occurring forces. On the other hand, there is the demand that the luff rope have an as small diameter as possible so as to ensure an optimum furling of the sail. Conventional roller reefing boom systems are not adapted to meet these contrary requirements.